As we are starting to see more cars with direct fuel injection, we are noticing that they have some intrinsic issues not found on standard port injected engines.
One major issue is carbon buildup, since we no long have fuel washing over the intake valves they tend to accumulate carbon due to the exhaust gas recirculation system. No, this does not mean you should remove EGR entirely.
What it does mean is that your intake valves will require an occasional cleaning, otherwise you may experience carbon buildup that is substantial enough to infringe upon the performance of your car.
Please see the attached document for complete instructions.